Missing analog signal

[Len14043]

Last night while driving around and listening to my HD radio, I tuned to WEBN at 102.7 and immediately noticed that it wasn't on the air. A few seconds later, the digital signal locked in and classic rock boomed out of the speakers. I then manually switched between the analog and digital modes and realized their analog signal was off the air but the digital portion was on. I knew the analog portion was off because rather than hearing a quiet carrier, another station on 102.7 was trying to poke through. I thought the digital signal had to have an accompanying analog signal to work in the hybrid mode, but apparently it doesn't. In this case, the digital signal backed up the analog signal.

 

[Mike Walker]

That's weird. Too often we hear of the digital signal going down while nobody at the station notices, but if their analog is going off while the guy (or gal) on duty slips out to the burger joint, or gets familiar with a groupie from the request line, THAT is, well, WEIRD.

 

[board_manager]

Several posts were relocated to TIO at the following URL

http://www.radio-info.com/smf/index.php/topic,64637.msg456587.html#msg456587

 

[4dude]

I thought the digital signal had to have an accompanying analog signal to work in the hybrid mode, but apparently it doesn't.

No it doesnt.........

All you should have heard was NOISE...... Im surprised you heard anything on that frequency in analog.....

 

[xmusicmatt]

Depending on how their plant is setup, its possible for the IBOC HD signal to stay on but the analog FM be off air.

 

[Tom Wells]

I would bet the situation is the other way on the AM, that the carrier must exist for sidebands to occur.
I don't think AM HD is intended in the hybrid mode to BE decodable as (with) suppressed or missing carrier, but with synchronous detection, it should be possible on the radio end.
It would certainly be the end goal of HD to eliminate carriers, naturally, because it is RF real estate.

 

[Len14043]

From Cincinnati, while listening to WXEG at 103.9 in HD from Dayton (32 miles), the radio faded to the analog signal from WRBI at 103.9 from Batesville Indiana (37 miles). Apparently the Batesville analog signal covered up the Dayton analog signal from the capture effect, but one or both sidebands at 103.7 and 104.1 from from the Dayton station was/were robust enough for detection.